There is a programme called SM64DSe, you can download it here: http://kuribo64.cjb.net/archive/board/thread.php?id=12
It can import .obj files in SUPER MARIO 64 DS roms and the results are really good!
You can check an old video I made: http://www.youtube.com/watch?v=qF98OwnnK9w&list=UUqmrpUDHWBUrwskKMr_aI_w&index=1
Well I don´t know if it is posible to do it in a Pokemon rom. =/
Thanks a lot for the tutorial!!
I've heard of the editor before, but I don't think the 3D Model types are the same. Since the games were developed at different times, newer filetypes have been made, so the formats would be vastly different. As well, the 3D engines in each game are vastly different, so one model probably wouldn't work on the other.
It'd be interesting to see if the creator of SM64DSe could perhaps make a model importer tool for the Pokémon DS games though.